Spark plug



Feb. 4, 1930. D. w. RANDOLPH ET AL SPARK PLUG Filed Nov. 5, 1928 MIIIIIIIIIIIIIIIII Patented Feb. il, i193@ ljetttltil DQNALD W. RANDLPHAND THUE G. MCDO''GAL, 0F FLINT, B/IICHLGAN, ASSXGNORS 'E0 A G SPAREPLUG COMPANY, 0F HINT,

MICHIGAL A COMPANY 02'? MECHIGMI SPARK PLUG' .Application filed November5, 1928. Scral No. 37,307.`

rlhis invention relates to electrical devices, such as spark plugs,which are subjected to heat and wherein fused quartz or other similarmaterial is employed as an insulator.

Since fused quartz is not only one of the best known non-conductors ofelectricity but also has a very low co-eli'icient of expansion, wherebyit may be exposed to sudden changes of temperature without liability offracture, it is highly desirable for use as an insulator core in themanufacture of spark plugs. However, fused quartz is diathermanous toradiations from a source of high temperature such as is present in thecombustion chamber of an internal combustion engine, and its resistanceto the passage' of such heat rays is so low t-hat it does itself notbecome hot. Being an excellent medium for the transmission of radiatedheat rays, the use of fused quartz as a spark plug insulator obviouslyallows the radiated heat rays, emanating from the explosions in theengine cylinder, to be transmitted to and absorbed by certain upperparts of the plug, as for instance, the terminal connector nut as wellas the current conducting lead wire, which, therefore, become intenselyhot. ln a comparatively short time such heat will have-a destructiveeffect on these parts and it is one of the objects of the presentinventionto provide a spark plug wherein the absorption of radiantenergy transmitted through the insulator core of high heattransmissibility by the upper and associated parts of the plug isetfectually prevented. To this end there is contemplated the provisionof a mirror-like surface to reflect or dissipate the heat rays beforethey are taken rup by the top parts of the plug. l F

The invention will be more fully comprehended upon reference to theaccompanying drawing wherein F ig. l is a vertical sectional yview of aspark plug embodying the present invention, Fig. 2 is a verticalsectional view of a spark plug illustrating a modication; l? ig. 3 is asectional view of the upper portion of the insulator core shown in Fig.2; and Fig. ds a detail view partly in section of the reflector employedin Fig. 2.

ln the accompanying drawing the reference character 1 indicates theouter shell having a screw-threaded portion for engagement within thecustomary spark plugopening in the cylinder head of an internalcombustion engine. l./"Vithin the shell is contained the insulator core2 of fused quartz or other similar diathermanous material, the packingrings or gaskets 3 and 4 serving to prevent leakage between theinsulator core and shell, and the flange 5 of the shell being crimped orspun over to maintain the parts in assembled relationship. Surrounded bythe insulator core is a central electrode or current-conducting wire 6,the lower end of which is spaced from the electrode 7 carried by theshell to form a sparking gap, and the upper end of the electrode 6 beingprovided with a terminal tip to receive a suitable connector, such asthe nut 8 for fastening the current conducting lead wire thereto.lnterposed between the connector element and the top of the insulatorcore is a washer 9, the under side of which, or that side contactingwith the top of the insulator core, having a burnished or platedsurfacefor reflecting heat waves away from the upper portions of theplug. Polished brass is an eX- cellent reflector of heat and if desiredthe washer 9 may be made of brass and its under surface highly polished.rl`he heat waves emanating in the engine combustion chamber and whichtravel in straight linesare transmitted through the insulator core tothe upper portion of the plug until they strike the inirror-like surfaceof the under side of the washer 9 when they are reflected back to theengine cylinder.. For illustrative purposes the path of the heat rays isindicated in the drawing by the double-headed arrows marked l0.

f lin Fig. 2 the insulator core ll inclosing the (i 'central electrode12 and carried by the' shell 13, is provided with a concave recess inits top surface in which is seated the concavoconvex or conical washer14, whose under surface is highly polished to provide a reflectingsurface for' the heat rays. In this case, the radiations from thecombustion chamber are transmitted through the insulator along the pathindicated by the arrows 15, striking the inclined reliector surface, andbeing thrown laterally-beyond the body of the insulator. v

From the above description, it will be apparent that there has beenprovided a spark plug wherein the heat rays are reflected away from theupper metallic parts of the plug, and

Since the rays are not absorbed by such parts,

the parts 'do not become hot and are thus `saved from deterioration anddamage.

While the invention has been described more or less specifically, it isto be understood that the invention is not limited to the exact detailsshown, but that such modication may be made as come within the scope ofappended claims.

We claim: v

1. In a spark plug for engines, a connector terminal, an electricalinsulator core of diatherinanous material and a reiiector interposedbetween the connector terminal and core to reiiect radiant energy andprevent its absorption by the terminal.

2.11m an electrical device, acurrent conductor, an insulator therefor ofa material transparent to heat rays, a connector associ'- ated with saidconductor and a reflecting surface between the connector and saidinsulator to reect heat waves away from the connector. l. v

3.' ln a device of the character described, a member of relatively lowresistance to the transmission of heat rays, a member of relatively highresistance to heat transmisson ositioned adjacent the first mentionedmeiner, and means interposed between said inembers to reiiect heatradiations transmitted thru said first mentioned member. y 4i. In aspark plug, an electrode, an electrical insulator surrounding theelectrode and having a relatively low resistance to heat radiations, aconnector device for said electrode adjacent the uper end of the4insulator and a heat wave 'reector interposed between the insulator andconnector device.

5. In a s ark plug, an insulator core transparent to eat radiations, anelectrode extending thru tlie core, and having a coilnector Jdevicelocated beyond the core, a

member interposed between the connector device and core and havin areecting surface abutting the core an eatending angularly to thel axisthereofto reect heat radiations transmitted thru the core and preventtheir absorption by the connector device.

6. lin a s ark plug, an electrode having a connector tip, an insulatorcore transparent to heat radiations,l surrounding the electrodeV andhaving a concave top surface directly heneath the connector tip and aconvex washer extending into the concavity having a mirror-like `surfaceabutting the top surface of the core, whereby heat radiationstransmitted thru the core and impinging on `said mirrorlike surfacearehreected angularly outside tures.

DONALD W. RANDOLPH. 'PAINE Gr MCDOUGAL. l

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